A minimum is required to program the beast.
You'll find this in the concise Stella Programmer's Guide.
You can download it in the PDF format Here (Local Mirror).
or have a look at the HTHL version Here.

In my opinion it's the best choice for testing VCS 2600 programs.
It's emulation level is near perfection : it's almost like using a real VCS 2600.
A lot of features are available.
DOS and Windows Exist. AFAIK It should be ported to linux soon.

I wrote this utility to draw Playfields for the Atari VCS 2600 and to save the pictures as datas code ready to be included into VCS 2600 programs.

TIA Playfield Painter V1.03

Features :

- DOS Program :
if used under Windows, for better performances it must be run into a full screen
DOS mode.

- TIA Playfield resolution emulation (WYSWYG) :
The picture displayed by the VCS using the code generated will have
the same resolution as the one displayed by the editor.

- Picture resolution : 2 playfields x 20 pixels x 192 lines (NTSC format).
NTSC has been chosen for best format compatibility. For PAL/SECAM programs,
empty scanlines may be added before and after the 192 scanlines of
the NTSC picture.

The Stella Mailing List Suscribe to the Stella Biglist to get the last informations about homebrew development and general VCS 2600 programming.
And don't forget to dig into the archives : it's a gold mine for any 2600 programmer !
Assembly In One Step A brief guide to programming the 6502 in assembly language.